In order to obtain detailed information on the conditions of a fire which has occurred, it is insufficient to use a single type of fire detector and fire detectors of different types, for example, an ionization type smoke sensor, a photoelectric smoke sensor, and a heat sensor, should be used in combination. In this case, the receiving unit of the fire detection system must determine the type of sensor before it can analyze the information that the sensor transmits.
In the conventional fire detection system, a separate address is allotted to each analog sensor, and all the address signals are constantly and successively sent out from a receiving unit to the analog sensors through an alarm line or some other kind of line. When an analog sensor receives the address signal allotted thereto, it converts its analog output into a quantized code which is sent out on the alarm line or some other line. Even the conventional fire detection system as described above can determine the type of sensor and judge and respond to the signal in accordance with the type of the sensor in question, since a separate address is allotted to each sensor and the information on the type of the sensor of which the address signal has been sent out is stored in the receiving unit.
In the conventional system, however, a complicated data-processing means has to be provided because it is necessary to provide a list for comparing the addresses and the types of the sensors. Recently such a list can be stored rather easily by means of a read only memory (ROM), but employment of a ROM impairs interchangeability between sensors of different types. Further, if the list is stored in a random access memory (RAM), a complicated program is required for rewriting the list upon any change in the sensor types.
The object of this invention is to provide a fire detection system wherein the above-mentioned defects of the conventional art are eliminated, the burden on the software for the receiving unit is reduced, and sensors can easily be replaced with those of different types.